Flapper or butterfly valves are well known for controlling the flow of a fluid through the valve. Those used in deposition systems and other tools (such as deposition vacuum chambers) are useful in controlling the flow of a vapor or gas from the tool so as to control the pressure in and/or flow of vapor and gas from the tool. The flapper is usually in the shape of a disk that is rotatable through 90° between a completely opened position wherein the plane of the disk is oriented 90° relative to the plane of the valve seat that defines the valve opening, and a completely closed position wherein the plane of the disk and valve seat are coplanar so that the flapper forms a closure with the valve seat of the valve opening. In some valves the flapper forms a sealed closure with the valve seat of the valve opening, while in others an unsealed closure is sufficient for the applications to which the valves are used. One common application for the flapper valve is to use the valve to maintain the pressure within a vacuum chamber by controlling the rate of exhaust of gases and vapors from the chamber.
During operation such as one in which the valve is used to control the pressure in or the rate of exhaust of gas and vapor from a vacuum chamber, the interior of the valve and the flapper are usually exposed to various vapors and gases that flow through it. Inevitably these vapors and gases can condense and leave deposits inside the valve, particularly at the edges and the side of the flapper facing the upstream flow of the controlled vapor or gas. These deposits can build to the point where they prevent the flapper from completely closing. This in turn affects the ability of the valve to control the rate of flow of gas and vapor through the valve when the valve needs to be positioned at or near the fully closed position. Valve removal is costly due to associated tool downtime and labor.
In order to extend the useable life of the valve before cleaning is required, many of these type valves include heaters embedded in the flapper to keep the gas and vapors above the solid and liquid phase so as to prevent the gases and vapors from depositing inside the valve. However, valve heating adds additional cost and complexity and may not be desirable with respect to the space limitations and power consumption in the space and application in which the valve is used.
Another approach to cleaning the interior of the flapper valve is to use the flapper of the valve to break up the deposits during a purging process by applying a relatively high enough torque to the flapper against the deposits so that the flapper can dislodge or break up the deposits. However, a high torque solution requires a higher cost motor and/or gearbox with high power/cost drive electronics for the motor.